This invention relates to a torque transducer assembly that attaches between a power tool or a rotating machine and a torque reaction device. This assembly provides a means for precisely measuring the torque output the tool is producing.
Preciseness, consistency and reporting of torque are very important to mass production operations, such as automobile assembly plants. Power tool applied torque to threaded fasteners must be consistent and within specifications. Industry typically incorporates the torque measuring or controlling device into the power tool. This often has been unsatisfactory because these attempts often lead to large, bulky, difficult to repair and expensive tools.
For example, in a typical power tool, torque is applied by a power source through a series of shafts and gear sets to the output spindle. This torque transducer measures the torque on the spindle through a torsionally resilient device strain gauges, a gear case, planet gears and ring gears. This circuitous path is expensive and difficult to incorporate into small power tools. Wear on the xe2x80x9cdrive trainxe2x80x9d components can effect the accuracy of the torque output readings. These devices really do not measure the torque the spindle of the tool is producing.
This assembly is a fixture that houses a torque measuring device. The assembly attaches to a torque reaction device such as a work station arm. A power tool attaches to the opposite end of the assembly. The assembly includes a hollow torsion tube that connects the tool to the reaction arm through the assembly. A torque transducer is attached to the side of the torsion tube. As the tool reacts to torque, it twists and this reaction is transferred to the torsion tube. The end of the torsion tube that is attached to the reaction device is fixed and therefore is not able to rotate. The transducer produces an electrical signal proportional to the amount of twisting that occurs. This signal is directly proportional to the output torque that the tool is producing.
A first end of the torque transducer is fixed to the torsion tube and unable to twist with respect to the torque output of the tool. A second end of the torque transducer is attached to the torsion tube and free to twist with respect to the torque output of the tool. The first end of the transducer is fixed adjacent the torque reaction device end of the torsion tube and the second end of the transducer is fixed adjacent the tool end of the torsion tube.
Since the reaction arm is large and heavy with respect to the tool, the first end of the transducer is unable to twist while the second end of the transducer is free to twist with the torque the tool is producing. In theory, the opposite is true except that the reaction arm end of the torsion tube does not twist because of the mass of the reaction arm.
The housing of the assembly is allowed to rotate nearly 360xc2x0 around the torsion tube on bearings or bushings. A handle is also attached to the housing. Since the operator holds the handle instead of the tool, the operators influence on the tool""s torque reaction in removed increasing the accuracy of the device. Flanges at the top and bottom of the torsion tube minimize the influence of thrust and side to side loading on the torque reading as well. Since the torsion tube is hollow, power for the tool (be it electrical or pneumatic) may pass through the center of the tool.